Traction control systems attempt to optimize vehicle acceleration and handling performance under low road/tire interface friction levels by controlling the slip of the driven wheels through wheel torque management via powertrain torque and possibly brake torque control. In certain conditions, aggressive traction control intervention is not required. Such conditions such as in large throttle tip-ins on dry roads may cause instantaneous short wheel spins. Other conditions such as driving across a rough road on a warm day also do not require aggressive traction control intervention. Such interventions are unintended. The feature that is common in such conditions is the environmental temperature. In warm conditions, snow and ice are not likely.
In typical traction control systems a slip target is set for the driven wheels. Thus, when the wheel speed of the driven wheel exceeds the slip target, traction control intervenes to maintain traction of the wheel. One example of this concept is set forth in U.S. Pat. No. 6,330,505. In the '505 patent, the target slip level defines the slip threshold. In the '505 patent, the outside air temperature is taken into consideration so that the target slip level is adjusted up or down. In high temperatures the target slip is raised and in low temperatures the target slip is lowered. The threshold remains at the target slip line. One drawback to such a system is that unintended activation may still be present.
It would therefore be desirable to prevent unintended activations in a traction control system when aggressive traction control system intervention is not required.